bio unit1 aos2

specialised cell

a cell that has become differentiated to perform a particular function

levels of organisation

specialised cell

tissue

organ

system

organism

example of levels of organisation

cardiac tisue

heart

circulatory systemm

human

endocrine system

consists of a network of ductless glands that release chemical messengers known as hormones into the bloodstream to regulate bodily functions

hormones

chemical messenger released from an endocrine gland that is transported via the blood to act on distant target cells

what do hormones do

influence the growth and development of body parts, cellular metabolism, reproduction and behaviour

maintain homeostasis

how do hormones work

1. specialised cells in endocrine gland secrete the hormone

2. hormone travels in the bloodstream to target cells in a tissue

3. binds to a specific receptor on the target cell which initiates a response

endocrine glands in the human body

pancreas, adrenal gland, thyroid gland, pineal gland and gonads (ovaries and testes)

pituitary

acts as the body’s ‘master gland’ as it tells other glands in the body what to do via chemical messages

thyroid

secretes hormones to regulate metabolic processes like growth and energy

thymus

responsible for production and maturation of immune cells

pancreas

exocrine tissue: produces and releases pancreatic juice into small intestine to aid digestion

endocrine tissue: islets of langerhans which controls blood glucose levels

islets of langerhans

contain specialised alpha and beta cells to maintain blood glucose levels

gonads

produce sex hormones

excretory system

maintains water balance within an organism and plays a major role in excretion of nitrogenous waste

nitrogenous wastes

toxic by product of metabolic reactions that cannot be stored and must be eliminated quickly

includes ammonia, urea and uric acid

parts of excretory system

renal artery

kidneys

ureter

bladder

urethra

renal vein

renal artery

brings blood into kidneys

kidneys

filter blood by removing urea and produces urine

ureter

trnsports urine from kidney to bladder

bladder

stores urine

urethra

transports urine from bladder to external environment

renal vein

carries the blood filtered by kidney back to vena cava

nephron

specialised structures within kidneys which filter blood and eliminate waste

fluid generated by each nephron is referred to as filtrate

two main parts: glomerulus and tubule

glomerulus

responsible for filtering the blood and surrounded by bowman’s capsule

tubule

consists of clewarly define regions that return important substances to the blood and keep waste for excretion

what happens in the nephron

filtration of water and solutes from the blood

reabsorption of water and solutes

secretion of solutes from the peritubular capillaries

vascular plants

have tissue moving water and minerals throughout the plant

grasses, flowering plants, ferns, trees, etc

non-vascular plants

don’t have tissue so cannot retain water or deliver it to other parts of the plant

mosses, some algae, liverworts, hornworts

features of vascular plants

systems/tissues maximise photosynthesis

must distribute materials from roots to tip

need transport systems (vascular tissue) to move materials

root system

below the soil surface

primary roots: grow down for strength and anchorage and can source water from deep underground

secondary roots: branch to the side to increase surface area for absorption

shoot system

above the ground

leaves: perform photosynthesis

stems: provide structural support and transport substances

leaf tissue

optimise light absorption and gas exchange

palisade mesophyll

site of photosynthesis and is located on the upper surface of the lead

spongy mesophyll

main site of gas exchange and is located on the lower surface of the leaf

stomata

on the underside of the leaf to maintain an open channel for gas exchange

vascular bundles

located centrally to allow for optimal access by leaf cells

cross section of leaf

cuticle

upper epidermis

palisade mesophyll

spongy mesophyll

xylem and ploem

lower epidermis

root tissue

absorbs water and dissolved minerals from soil

outer epidermis: water and minerals enter

cortex: improves aeration

vascular tissue: transports absorbed minerals

xylem

hollow tube composed of an outer layer of dead cells with gaps to facilitate water exchange

phloem

organic molecules that are produced in photosynthesis are transported in the phloem vessels throughout plant in both directions

transpiration

movement of water throughout a plant from the roots to its evaporation through the leaves into atmosphere

root uptake

roots have protrusions called root hairs which increases surface area for absorption of water/minerals

xylem transport

cohesion: attraction between 2 particles of the same substance. causes water molecules to be dragged up the xylem towards the leaves in a continuous stream

adhesion: attraction between 2 particles of different substances. as water molecules move up capillaries they pull inwards on the xylem walls to generate further tension

stomata for water regulation

guard cells: close the opening by become flaccid

can open the stomata when they become turgid

stomatal pores

responsible for gas exchange in the leaf

transpiration rates are higher when pores are open

factors that affect rate of transpiration

temperature

wind

humidity

homeostasis

maintenance of a relatively stable internal environment within narrow limits despite changes in the external environment

why is homeostasis important

allows important life processes such as growth, tissue repair and reproduction to occur

if changes are out of tolerance levels for too long it will cause body system to malfunction → illness/death

what organs regulate body temp

hypothalamus - thermoreceptors

pituitary gland

thyroid

stimulus response body temp

s: body temp rises above 37

r: thermoreceptor in hypothalamus

cc: brain - hypothalamus

e: blood vessels dilate and sweat glands activate

r: temperature goes down to 37

hypothalamus

located at the base of the brain, above the brainstem and works to regulate core body temperature. it can detect when the body’s temperature is outside of its normal range and triggers the relevant response. this includes shivering to warm up the body and sweating to cool down.

pituitary

is located at the base of the brain, behind the bridge of the nose and below the hypothalamus. it is also called the “master gland” as it produces hormones that influences other endocrine glands and tissues.

thyroid gland

small gland located at the front of the neck which produces thyroxine to regulate metabolism and heat production. this hormone increases metabolism which generates heat in order to maintain core body temperature

blood glucose optimal levels

3.5-8mmol/L

stimulus response blood glucose

s: blood glucose levels change

r: alpha detect low glucose, beta cells detect high glucose

cc: pancreas

e: insulin released from beta cells into bloodstream, glucagon release from alpha cells which stimulates liver to breakdown glycogen into glucose

r: blood glucose levels return to normal

associated organ structures in blood glucose

liver

pancreas

islets of langerhans

alpha/beta cells

type 1 diabetes

occurs when body can no longer produce insulin, meaning that beta cells cannot function

glucose stays in the blood instead of being absorbed by cells and body cannot maintain stable glucose levels

lead to high blood sugar

hypoglycaemia

commonly occurs in type 1 diabetics if insulin is mismanaged (take too much)

also caused as consequence of improper dietary management or extended physical exertion

sweating, hunger, fatigue

hyperthyroidism

excessive production of thyroid hormones

causes abnormally high metabolic rate as thyroid hormones control metabolism

weight loss, increased heart rate, heat intolerance

enzymes

proteins that catalyse reactions by lowering activation energy

digestive enzymes

breakdown large food molecules into smaller molecules that can be absorbed into small intestime

types of digestive enzymes

amylase

protease

lipase

amylase

breaks down starch into glucose

protease

breaks protein into amino acids

lipase

breaks fats down into fatty acids and glycerol

digestive system

involved in the breakdown and absorption of ingested food materials

steps of digestive pathway

ingestion

physical and chemical breakdown

absorption

egestion

physical digestion

increases surface area of food to allow for chemical digestion

teeth break down large pieces of food into smaller pieces

muscular churning (peristalsis) of stomach

emulsification of fats by bile

chemical digestion

further breaks down food small enough to be absorbed

includes acids, enzymes and other chemicals

alimentary canal

contains oesophagus, stomach, small and large intestine

oesophagus

hollow tube connecting the oral cavity to stomach

moves food via peristalsis

stomach

temporary storage tank where food is mixed in an acidic environment

chemical and mechanical digestion

churning of stomach

gastric juice

small intestine

high sa:v ratio where usable nutrients are absorbed

peristalsis occurs throughout entire intestine

7m length 4.5km sa

how is small intestine sa:v increased

villi and microvilli

large intestine

water and dissolved minerals are absorbed

accessory glands

salivary glands

pancreas

liver

gall bladder

pancreas - digestive

releases enzymes into small intestine and secretes hormones

liver

takes raw materials from intestine and metabolises them

responds to glucagon which breaks down glycogen into glucose

gall bladder

stores bile produced by the liver and releases it into the small intestine

neutralises stomach acid